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Challenge: Processing problems at a crude oil terminal in Trinidad caused as much as 1,500 bbl/day of “slop oil” waste to be generated. Produced fluids from offshore platforms are piped to the onshore terminal where traditional techniques of chemical dehydration and settling time are employed. The slop is formed in the interface between the separated crude oil and the free water, and comprises a stable emulsion of oil, water and fine solids. The slop waste is partially recycled back into the upstream system creating separation problems in the crude dehydration process. Valuable tank space has to be used to store this slop which not only reduces the efficiency of the Production operations but also represents unrealized revenue for the operator.

Solution: Production Waste Management experts from M-I SWACO used simulation and characterization techniques to design a mechanical-chemical separation system with two stages of centrifugation to split the slop oil emulsion. Initially the oil is heated and homogenized and then pumped to a decanter centrifuge which takes out any larger solid particles from the liquid. In the second stage a disk-stack centrifuge, utilizing in excess of 5,000 G force, is able to separate clean crude oil from the water and fine solids that make up the stubborn emulsion. Chemicals specifically designed by the Production Technologies specialists from M-I SWACO are used to enhance the separation performance and increase the treatment system throughput. Clean crude oil recovered from the slop waste is pumped to the client’s export tanks while the separated water is delivered to the onsite water treatment plant and the solids are sent for disposal.

Result: Clean crude oil from the M-I SWACO system was recovered to <0.5%BS&W (basic sediment and water), i.e., direct export specification. In the first 8 months of operation over 50,000 bbl of clean crude oil has been recovered from the slop waste and returned to the client. The system is flexible enough to treat both fresh slop oil from the daily production and also the aged slop oil from the storage tanks without reconfiguration of the process. Crude dehydration in the upstream production system is now faster as a result of the elimination of the slop waste recycling. The system operates 24-hr per day 7 days per week, and with our policy of continuous improvement, an upgrading program is underway to further increase the system throughput.